1. Estimation of Kidney Function Richard C. Walls 07-16-2013

2. Importance of Kidney Function Kidney responsible (in part/whole) for excretion of many medications from the body t 1/2 of renally cleared medications prolonged with decreasing kidney function – Vancomycin: 5-11 hours w/normal function – Vancomycin: 8-10 days in ESRD Potential for medication error – Drug accumulation & toxicity – Overly rapid clearance & subtherapeutic doses

3. Importance of Kidney Function Medications often require dose adjustment when eGFR < 60 ≈40% of adults >70 years old have eGFR < 60 This population uses 34% of all prescription drugs

4. Estimating Kidney Function

7. Dowling Study Objective: To evaluate how accurately different estimates of renal function reflect actual creatinine clearance. Retrospective review of data collected as a part of the Baltimore Longitudinal Study of Aging

8. Dowling Study CrCl estimated/measured via – Measured 24-hour creatinine clearance (mCl Cr ) – Cockcroft-Gault (CG) – Cockcroft-Gault S Cr < 1.0 rounded to 1.0 (r-CG) – Modification of Diet in Renal Disease (MDRD) – Chronic Kidney Disease Epidemiology Collaboration (CKD- EPI) Estimates compared for – Bias from mCl Cr – Variance ratio to mCl Cr – Dosage discordances from CG labeling

9. Dowling Study - Population Patients: 269 total – 140 women – 129 men Age, yrs: 81 ± 6 S Cr : 1.1 ± 0.4 – 103 subjects < 1.0 – Avg 8.0 ± 0.1 Race: 85% white BMI – Only 28 patients > 30 – No patients > 40 Overt signs of renal failure/dialysis excluded

10. Dowling Study - Results MeasurementReturned ValueBias from mCl Cr Variance Ratio to mCl Cr mCl Cr 52.8 ± 12.6n/a CG49.6 ± 14.3-3.2 ± 14.11.3 MDRD65.5 ± 18.512.8 ± 15.12.2 CKD-EPI59.9 ± 16.17.1 ± 15.11.63

11. Dowling Study - Results Patients w/S Cr < 1.0 MeasurementReturned Value mCl Cr 56.2 ± 11.5 CG55.8 ± 15.0 r-CG44.1 ± 10.2

12. Dowling Study - Results